Hi. I want simulate a two stage centrifugal pump, by Fluent. Pump contains: inlet that is a bent pipe, two impellers, diffusers and outlet is a dual volute. I want use Multiple Reference frame (MRF), but, whereas the pump geometry are 3-D and complex shape, I have many problem for simulate in FLUENT. I need help. Problems are in the below: 1- Is a correct MRF model for use complete pump? 2- What is correct turbulence model? Standard k-e? Or RNG k-e? Or Realizable k-e? 3- What suitable “Turbulent Intensity” for pump inlet? 2% or more percent? 4- What suitable “Under relaxations” for convergence a solution? 5- What suitable method for ” Discretization pressure” (with consideration to model)? Standard? Or PRESTO! ? or etc? 6- Other problem is description Boundary conditions for moving zones(rotational zones). I don’t Know what coordinate input for “ Rotation-Axis- Origin” for positions: impeller1 and impeeler2 and other geometry, because any geometry have different center point. For example center point for impeller 1 is a (0, 0, 3.33) and center point for impeller is a (0, 0,-143).(center coordinate is a (0,0,0)). Please help me. Thanks.